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** 	TITLE:		us2020_polls		                                          ** 	
**	AUTHOR:	    Philippe Mongrain                                             **
**  DATE:	    October 2022 						                          **	
**  VERSION:	Stata 16					                                  **	
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* Version control

version 16.0

* Import data

import excel surveys, firstrow sheet(us2020) clear
destring _all, replace

* Generate survey date

format %tdMon_DD,_CCYY polldate

* Generate election date

gen edate = 20201103

gen electiondate = date(string(edate,"%8.0f"),"YMD") 

format %tdMon_DD,_CCYY electiondate

* Time of survey

gen time = (electiondate - polldate) - 1

* Generate mean vote intention value by day

drop if jorgensen == . & howie == . & others == .

bysort time : egen trumpvote = mean(trump)
bysort time : egen bidenvote = mean(biden)
bysort time : egen jorgensenvote = mean(jorgensen)
bysort time : egen howievote = mean(howie)
bysort time : egen othersvote = mean(others)

sort time

* Drop duplicates

duplicates tag polldate, gen(dup)
duplicates drop polldate, force
drop dup

* Reshape the dataset

rename trump v_trump
rename biden v_biden
rename jorgensen v_jorgensen
rename howie v_howie
rename others v_others

reshape long v_, i(polldate) j(party) string

rename v_ vote

keep polldate electiondate party vote poll time

order poll polldate electiondate time party vote

* Generate rank of parties

gsort polldate -vote

bysort polldate : gen rank = _n

gen first = party if rank == 1
gen second = party if rank == 2
gen third = party if rank == 3

bysort polldate : gen winner = first[1]
bysort polldate : gen runnerup = second[2]
bysort polldate : gen thirdplace = third[3]

* Generate poll margin

bysort polldate : gen pollmar = vote[1] - vote[2]

* Drop duplicates

duplicates tag polldate, gen(dup)
duplicates drop polldate, force
drop dup

* Misleading poll

gen misleading = 0 if winner == "biden" & pollmar >= 1
replace misleading = 1 if misleading!=0

* Save

drop if time == 0 | time == .

keep polldate pollmar misleading time

save "us2020_polls.dta", replace